Objective: To characterize spatiotemporal trends, age-period-cohort dynamics, and health inequalities of HIV/AIDS in Asia from 1990 to 2023, and project the burden to 2040, with a specific focus on older adults. Methods: Using Global Burden of Disease (GBD) 2023 data from 49 Asian countries and territories, we estimated prevalence, incidence, mortality, and disability-adjusted life years (DALYs), with age-standardized rates (ASR). Joinpoint regression assessed temporal trends. Age-period-cohort (APC) effects were examined, and Das Gupta decomposition identified drivers of burden change. Frontier analysis and health inequality indices (Slope Index of Inequality, Concentration Index) were linked to the Socio-demographic Index (SDI). Bayesian APC models projected the burden from 2024 to 2040. Results: In 2023, approximately 4.70 million people were living with HIV/AIDS in Asia (ASPR: 90.18/100,000). Southeast Asia had the highest prevalence and mortality, while Central Asia had the highest incidence (ASIR: 22.22/100,000). From 1990 to 2023, ASPR increased (EAPC=4.64%), whereas ASIR declined (EAPC=-1.04%). Adults aged ?65 years showed a persistent ASPR increase throughout the entire period. The Slope Index of Inequality shifted from positive (10.80 in 1990) to negative (-97.57 in 2023), indicating absolute burden concentration in lower-SDI regions. Projections to 2040 indicate that ASPR will continue rising, while ASIR, ASMR, and ASDR will decline. Conclusions: Asia faces a dual transition characterized by rising prevalence, aging survivors, and widening absolute health inequalities. Future strategies must move beyond infection control toward integrated, life-course management specifically targeting the growing chronic disease burden among older people living with HIV.